JP5720693B2 - Method for producing conductive copper particles - Google Patents

Description

  The present invention relates to conductive copper particles, a method for producing conductive copper particles, a composition for forming a conductor, and a substrate with a conductor.

  As a manufacturing method of a substrate with a conductor having a conductor film of a desired wiring pattern such as a printed circuit board, a method of applying a silver paste containing silver particles in a desired wiring pattern on a substrate and curing it is available. Are known. However, the silver conductor film tends to cause a short circuit due to ion migration. For this reason, from the viewpoint of the reliability of electronic devices, it has been studied to form a conductor film using a copper paste instead of a silver paste. However, copper particles are easily oxidized, and an oxide film is easily formed on the surface. Therefore, the conductor film using copper particles tends to have a high volume resistivity, and its change with time is large.

The following methods (1) to (3) are known as methods for producing conductive copper particles that form a conductor film having a low volume resistivity.
(1) A method of treating conductive powder made of copper or a copper alloy with an aqueous solution containing an acid, a reducing agent, and an alkali metal salt of a fatty acid having 8 or more carbon atoms (Patent Document 1).
(2) A method in which hypophosphorous acid is added to an aqueous copper salt solution to precipitate copper hydride fine particles, and the copper hydride fine particles are thermally decomposed to obtain copper fine particles (Patent Document 2).
(3) In a solution containing copper ions, 0.05 mol or more (1250 mass ppm or more) of chloride ions is contained with respect to the copper ions, and reduced at a pH of 10 to 12.5. A method for producing copper particles having irregularities (Patent Document 3).

Japanese Unexamined Patent Publication No. 2007-184143 Japanese Laid-Open Patent Publication No. 2-294417 Japanese Unexamined Patent Publication No. 2007-169770

However, although the conductor film using the copper particles produced by the method (1) has excellent conductivity immediately after the film formation, the volume resistivity is greatly increased by storage in the air at room temperature. It cannot be used for wiring.
According to the method (2), particles obtained by agglomerating copper hydride fine particles can be obtained. However, when the particles produced by this method are used as a conductor film, the conductivity is insufficient, and room temperature, in air Volume resistivity increases with storage.
The conductor film using the copper particles produced by the method (3) has a large volume resistivity even immediately after the film formation, and the volume resistivity increases with time, so it cannot be used for wiring of electronic equipment.

  The present invention provides a conductive copper particle capable of forming a conductor film having a low volume resistivity and a small change with time, a method for producing the conductive copper particle, a composition for forming a conductor containing the conductive copper particle, and It aims at providing the base material with a conductor which has a conductor film formed with the said composition for conductor formation.

The conductive copper particles of the present invention contain 50 to 1000 ppm by mass of chlorine atoms with respect to the total mass of the particles, and the chlorine atoms are present in a water-insoluble form.
The conductive copper particles of the present invention preferably have an average particle diameter of 0.01 to 20 μm.

The composition for forming a conductor of the present invention includes the conductive copper particles of the present invention and a solvent. Moreover, it is preferable that the composition for conductor formation of this invention contains a resin binder.
The base material with a conductor of the present invention has a base material and a conductor film formed on the base material by the conductor forming composition of the present invention.

  The method for producing conductive copper particles of the present invention includes a step of reducing at least one of copper particles and copper (II) ions in a reaction system containing chloride ions, having a pH of 3 or less and a redox potential of 220 mV or less. It is the method which has.

If the conductive copper particles of the present invention are used, a conductor film having a low volume resistivity and a small change with time can be formed.
Moreover, according to the manufacturing method of the electroconductive copper particle of this invention, the electroconductive copper particle which can form a conductor film with a low volume resistivity and a small time-dependent change is obtained.
Moreover, the composition for forming a conductor of the present invention includes the conductive copper particles of the present invention, and can form a conductor film having a low volume resistivity and a small change with time.
Moreover, the base material with a conductor of this invention has a low volume resistivity of a conductor film, and its temporal change is small.

<Conductive copper particles>
By using the conductive copper particles of the present invention, a conductor film having a low volume resistivity and a small increase in volume resistivity over time can be formed. The reason why the conductor film having the above effect can be formed is not necessarily clear, but is estimated as follows.

  The electroconductive copper particle of this invention contains the chlorine atom which exists in a water-insoluble form. In the present specification, the phrase “a chlorine atom is present in a water-insoluble form” means that a chloride ion concentration measured by a measurement method described later is 10 mass ppm or less.

  In order to obtain the conductive copper particles of the present invention, copper (II) ions (divalent copper ions) are reduced. In the process, it is considered that the copper (I) ions (monovalent copper ions) are routed. When copper (I) ions are generated, if an appropriate amount of chloride ions, which are monovalent anions, are present in the vicinity, both react quickly to form copper (I) chloride on the surface of the conductive copper particles. It is thought. Therefore, it is considered that the oxidation of the conductive copper particle surface is suppressed and a low volume resistivity can be obtained. Further, copper (I) chloride has extremely low solubility in water and low affinity with water, so that deterioration due to moisture in the air is small. Therefore, it is considered that an excellent effect that an increase in volume resistivity can be suppressed for a long time even after a substrate with a conductor is obtained.

  As described above, it is considered that the conductive copper particles of the present invention contain chlorine atoms in a form with extremely low solubility in water. However, since it is difficult to identify copper chloride (I) in the conductive copper particles, it is defined as water-insoluble because the chloride ion concentration measured by the measurement method described later is 10 mass ppm or less. .

  Content of the chlorine atom in electroconductive copper particle is 50-1000 mass ppm with respect to the total mass of electroconductive copper particle, and 80-300 mass ppm is preferable. If content of a chlorine atom is more than the said lower limit, progress of the surface oxidation of a copper particle can be suppressed. If content of a chlorine atom is below the said upper limit, a conductor film with small volume resistivity can be formed. The content of chlorine atoms in the conductive copper particles is measured by fluorescent X-ray analysis.

(Measurement method)
1. The content of chlorine atoms in the conductive copper particles is measured by fluorescent X-ray analysis.
2. If all the chlorine atoms contained in the conductive copper particles are eluted in the distilled water, the conductive copper particles in an amount such that the concentration of chloride ions contained in the distilled water is 100 ppm by mass are added to the distilled water. Immerse.
3. Distilled water in which conductive copper particles were immersed was stirred at 20 ° C. for 5 seconds at 1000 rpm using a test tube mixer (manufactured by ASONE, HM-01), and then the chloride ion concentration eluted in the distilled water was determined. taking measurement. Here, the distilled water to be used is distilled water whose dissolved oxygen concentration is adjusted to 1 mass ppm or less.
Note that the dissolved oxygen concentration is 1 mass ppm or less because copper (I) chloride (monovalent copper) present in the conductive copper particles is affected by oxidation by dissolved oxygen. This is to prevent the change to copper.

The amount of surface oxygen represented by the ratio of the surface oxygen concentration (unit: atom%) to the surface copper concentration (unit: atom%) of the conductive copper particles is preferably 0.5 or less, and more preferably 0.3 or less. If the amount of surface oxygen is less than or equal to the upper limit value, the contact resistance between the conductive copper particles becomes smaller, and the conductivity of the conductor film is improved.
Note that the surface oxygen concentration and the surface copper concentration of the conductive copper particles are determined by X-ray photoelectron spectroscopy. Measurements are made over a range from the particle surface to the center to a depth of about 3 nm. If the measurement is performed in this range, the state of the particle surface can be sufficiently grasped.

The form of the conductive copper particles of the present invention is not particularly limited. Examples of the conductive copper particles of the present invention include the following conductive copper particles (A) to (E).
(A) Copper particles having a water-insoluble form of chlorine atoms and having an average particle diameter of 1 μm or more.
(B) Primary particles containing chlorine atoms in a water-insoluble form, and secondary particles containing chlorine atoms in a water-insoluble form on the surface of copper particles having an average particle diameter of 1 μm or more. Copper composite particles to which copper hydride fine particles having an average particle size of 20 to 350 nm are attached.
(C) Secondary particles containing chlorine atoms in a water-insoluble form, and the fine particles of copper hydride having an average particle diameter of 10 nm to 1 μm.
(D) Primary particles containing chlorine atoms in a water-insoluble form, and secondary particles containing chlorine atoms in a water-insoluble form on the surface of copper particles having an average particle diameter of 1 μm or more. Copper composite particles to which copper fine particles having an average particle diameter of 20 to 350 nm are attached.
(E) Secondary particles containing chlorine atoms in a water-insoluble form, and copper fine particles having an average particle diameter of 10 nm to 1 μm.
The conductive copper particles (B) and the conductive copper particles (D) are conductive copper particles composed of a combination of primary particles and secondary particles, and the conductive copper particles (A), (C) and (E) are , Conductive copper particles composed of only primary particles or only secondary particles.

  When the copper hydride fine particles are heated, the copper hydride is converted into metallic copper to form copper fine particles. That is, the conductive copper particles (B) become conductive copper particles (D) by heating. Moreover, electroconductive copper particle (C) turns into electroconductive copper particle (E) by heating.

The conductive copper particles of the present invention preferably have a surface coated with an organic material for the purpose of preventing oxidation and improving the fluidity of the conductor-forming composition. The “coating” includes not only the case where the organic material covers the entire surface of the conductive copper particles, but also the case where the organic material partially covers the surface. Furthermore, it includes not only the case where the organic substance is bonded to the surface of the conductive copper particles but also the case where it is coordinated.
Examples of the organic substance include carboxylic acid, amine, imidazole compound, and triazole compound.
Examples of the carboxylic acid include oleic acid, stearic acid, myristic acid, dodecanoic acid, decanoic acid, octylic acid, octanoic acid, hexanoic acid, benzoic acid, salicylic acid, and abietic acid.
Examples of the amine include oleylamine, stearylamine, myristylamine, dodecylamine, decylamine, octylamine, hexylamine, and aniline.
As the organic substance, when preparing a composition for forming a conductor containing a resin binder together with conductive copper particles, carboxylic acid is preferable from the viewpoint of wettability between the conductive copper particles and the resin, oleic acid, salicylic acid, Abietic acid is more preferred. The wettability is the affinity between the particle surface and the resin by changing the interfacial energy.

  The average particle diameter of the conductive copper particles of the present invention is preferably 0.01 to 20 μm, and may be appropriately adjusted within this range according to the shape of the conductive copper particles. As for an average particle diameter in case an electroconductive copper particle contains a primary particle, 1-10 micrometers is more preferable. Moreover, 0.01-1 micrometer is preferable and, as for an average particle diameter in case an electroconductive copper particle consists only of secondary particles, 0.02-0.4 micrometer is especially preferable. If the average particle diameter of electroconductive copper particle is more than the said lower limit, the flow characteristic of the composition for conductor formation containing this electroconductive copper particle will become favorable. If the average particle diameter of the conductive copper particles is not more than the above upper limit value, it becomes easy to produce fine wiring.

  The average particle diameter in this specification can be calculated | required as follows with the shape of electroconductive copper particle. When determining the average primary particle size of primary particles, the particle size of 100 particles randomly selected from the image of a scanning electron microscope (hereinafter referred to as “SEM”) is measured, and the particle size is calculated. Calculated by averaging. Secondary particles are calculated by measuring the particle size of 100 particles randomly selected from a transmission electron microscope (hereinafter referred to as “TEM”) image and averaging the particle sizes. The

  When the copper particles are not spherical, if they are primary particles, the average value of the major and minor diameters of the copper particles is taken as the particle size. When the particles are secondary particles, the average value of the long diameter of the secondary particles and the short diameter of the secondary particles is taken as the particle diameter.

  Moreover, in the case of electroconductive copper particle (B), the electroconductive copper particle (B) whole containing the copper particle which is a primary particle, and the copper hydride microparticle which is the secondary particle adhering to this copper particle is carried out by SEM. Observe and the average value of the major axis and minor axis including the secondary particles is taken as the particle diameter. Similarly, in the case of conductive copper particles (D), the entire conductive copper particles (D) including copper particles as primary particles and copper fine particles as secondary particles attached to the copper particles are observed by SEM. The average value of the major axis and minor axis including the secondary particles is taken as the particle diameter.

<Method for producing conductive copper particles>
The conductive copper particles of the present invention have a step of reducing at least one of copper particles and copper (II) ions in a reaction system containing chloride ions, having a pH of 3 or less and a redox potential of 220 mV or less. It can be manufactured by a method. Hereinafter, a specific manufacturing method is demonstrated for every kind of form of the electroconductive copper particle to manufacture.

(Method for producing conductive copper particles (A))
Examples of the method for producing the conductive copper particles (A) include a method having the following steps (α-1) and (α-2).
(Α-1) Copper particles that are primary particles (hereinafter referred to as “copper particles (a1)”) are dispersed in a dispersion medium, contain chloride ions, have a pH of 3 or less, and a redox potential of 220 mV or less. A step of obtaining conductive copper particles (A) by reducing copper particles (a1) in a reaction system (hereinafter referred to as “reaction system (α)”).
(Α-2) A step of separating the conductive copper particles (A) from the reaction system (α).

Step (α-1):
Copper particles (a1) are dispersed in a dispersion medium, a compound that dissolves in the dispersion medium to generate chloride ions is added, the pH is 3 or less, a reducing agent is added, and a reaction system (α) is formed. Then, the copper particles (a1) are reduced. Here, during the reduction reaction, the redox potential of the reaction system (α) is adjusted to be 220 mV or less. The surface of the copper particles (a1) is usually oxidized to form an oxide film made of cuprous oxide. In the reaction system (α) of the step (α-1), the cuprous oxide of the oxide film of the copper particles (a1) is reduced. Moreover, after adding the compound which melt | dissolves in a dispersion medium and produces | generates a chloride ion, makes pH 3 or less, and adds a reducing agent, a copper particle (a1) is disperse | distributed and reaction system ((alpha)) is formed. Also good. Again, during the reduction reaction, the redox potential of the reaction system (α) is adjusted to be 220 mV or less.

  As a copper particle (a1), the well-known metal copper particle generally used for the conductor formation composition called a copper paste is mentioned. The metallic copper particles are primary particles. The particle shape of the copper particles (a1) may be spherical, or may be a plate shape, a scale shape, or the like.

  Since the surface of copper particles is easily oxidized, generally, commercially available copper particles are often surface-treated with a long-chain carboxylic acid such as stearic acid, oleic acid or myristic acid for the purpose of preventing surface oxidation. Copper particles that have been surface-treated with a long-chain carboxylic acid have a hydrophobic surface, and therefore tend to aggregate in a highly polar dispersion medium such as water described below. Therefore, when using the copper particle surface-treated with the long chain carboxylic acid, it is preferable to remove the long chain carboxylic acid on the surface before the step (α-1). The removal of the long-chain carboxylic acid on the surface can be carried out by treating the copper particles with a degreasing agent or heat-treating in an alkaline aqueous solution.

  As will be described later, the medium for the copper particles (a1) is a highly polar medium such as water or a mixed medium of water and alcohol. From the viewpoint of improving the dispersibility of the copper particles (a1) in these highly polar dispersion media and easily suppressing the aggregation of the copper particles, the copper particles (a1) are preferably copper particles pretreated with a dispersant. . A dispersing agent is carry | supported on the surface of a copper particle, and makes the surface hydrophilic. Even if it is a copper particle surface-treated with long-chain carboxylic acid, the copper particle by which the surface was hydrophilized by the pre-processing by a dispersing agent is obtained.

As the dispersant, various water-soluble compounds having chemical adsorption properties to copper particles can be used. Examples of the water-soluble compound include short-chain aliphatic carboxylic acids, water-soluble polymer compounds, chelating agents, and the like.
As the short-chain aliphatic carboxylic acids, aliphatic monocarboxylic acids such as aliphatic monocarboxylic acids having 6 or less carbon atoms, aliphatic hydroxy monocarboxylic acids and aliphatic amino acids; aliphatic polycarboxylic acids having 10 or less carbon atoms, Aliphatic polycarboxylic acids such as aliphatic hydroxypolycarboxylic acids are more preferred.
Examples of the water-soluble polymer compound include polyvinyl alcohol, polyacrylic acid, polyvinyl pyrrolidone, hydroxypropyl cellulose, propyl cellulose, and ethyl cellulose.
Examples of the chelating agent include ethylenediaminetetraacetic acid, iminodiacetic acid and the like.

  As the dispersant, short-chain aliphatic carboxylic acids are preferable, and aliphatic polycarboxylic acids having 8 or less carbon atoms such as glycine, alanine, citric acid, citric anhydride, malic acid, maleic acid, malonic acid, and the like are more preferable. Particularly preferred are aliphatic dicarboxylic acids such as malic acid and maleic acid, or tricarboxylic acids such as citric acid.

  The pretreatment can be carried out by dissolving the dispersant in a solvent such as water and adding the copper particles to this solution and stirring. Thereby, a dispersing agent couple | bonds with the copper particle surface. The pretreatment is preferably performed by replacing the inside of the treatment container with an inert gas from the viewpoint of suppressing the oxidation of the surface of the copper particles. Nitrogen gas, argon gas, etc. can be used as the inert gas. After the pretreatment, the solvent is removed and, if necessary, washing with water or the like is performed to obtain copper particles whose surface has been hydrophilized by the pretreatment.

The pretreatment can be performed even under heating. By performing the pretreatment under heating, the processing speed is improved. The heating temperature is preferably 50 ° C. or higher and not higher than the boiling point of a solvent such as water (or lower boiling point when a low-boiling dispersant is used). The heating time is preferably 5 minutes or more. Moreover, since heating for a long time is not economical, the heating time is preferably 3 hours or less.
The amount of the dispersant used for the pretreatment is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the copper particles before the pretreatment.

  The average particle diameter (average primary particle diameter) of the copper particles (a1) is preferably 1 to 20 μm. Thereby, the electroconductive copper particle (A) whose average particle diameter (average primary particle diameter) is 1-20 micrometers is easy to be obtained.

  The concentration of the copper particles (a1) in the reaction system (α) (100% by mass) is preferably 0.1 to 50% by mass. If the density | concentration of a copper particle (a1) is 0.1 mass% or more, the usage-amount of a dispersion medium can be suppressed and the production efficiency of an electroconductive copper particle (A) will become favorable. If the density | concentration of a copper particle (a1) is 50 mass% or less, since the influence of aggregation of copper particles (a1) will become smaller, the yield of electroconductive copper particle (A) tends to become high.

  As the dispersion medium, water or a medium containing water as a main component and containing alcohols such as methanol, ethanol, 2-propanol, and ethylene glycol can be used, and water is particularly preferable. In addition, water as a main component means that water is 70 mass% or more in 100 mass% of the dispersion medium.

  The concentration of chloride ions in the reaction system (α) is preferably 5 to 100 ppm by mass, and more preferably 10 to 50 ppm by mass with respect to the total mass of the reaction system (α). If the concentration of chloride ions is equal to or higher than the lower limit, an appropriate amount of chloride ions is present on the surface of the copper particles (a1) in the course of the reduction reaction. It is easy to obtain conductive copper particles (A) having a low resistivity. Moreover, if the density | concentration of a chloride ion is below the said upper limit, it will be easy to suppress that there is too much quantity of copper (I) in electroconductive copper particle (A), and electroconductivity falls.

  The concentration of chloride ions can be adjusted by adjusting the amount of the compound that dissolves in the dispersion medium of copper particles (a1) to produce chloride ions. As a compound that generates chloride ions, hydrochloric acid, sodium chloride, potassium chloride, copper (II) chloride, and the like can be used as appropriate.

The pH of the reaction system (α) is 3 or less, preferably 0.5 to 3, and more preferably 0.5 to 2. When the pH of the reaction system (α) is 3 or less, the oxide film on the surface of the copper particles (a1) is smoothly reduced. Further, it is known that there is a stable region of copper (I) chloride at a specific oxidation-reduction potential in a low pH region of pH 3 or less (Hiroaki Nakano et al., Journal of MMIJ, No. 123 (2007)). 33-38). From this, in the step (α-1), when the oxide film is reduced, copper (I) chloride is formed on the surface of the copper particles (a1), and as a result, a conductive material containing chlorine atoms in a water-insoluble form. It is considered that the conductive copper particles (A) are obtained.
Moreover, if pH is 0.5 or more, it will be easy to suppress that a copper (II) ion elutes excessively from a copper particle, and it will be easy to implement the surface modification of a copper particle (a1) smoothly.

The pH of the reaction system (α) is adjusted with a pH adjuster.
An acid can be used as the pH adjuster. As the acid of the pH adjusting agent, carboxylic acids that are soluble in water or alcohols such as formic acid, citric acid, maleic acid, malonic acid, acetic acid, propionic acid and the like are preferable. The carboxylic acid may be adsorbed on the surface of the copper particles and may remain on the surface of the conductive copper particles (A) after the reduction treatment. The remaining carboxylic acid can be expected to protect the surface of the conductive copper particles (A) and suppress the oxidation. As the acid of the pH adjuster, formic acid is particularly preferable among the carboxylic acids. Since formic acid is a compound having an aldehyde structure (—CHO), it has reducibility. Therefore, the formic acid remains on the surface of the conductive copper particles (A) after the reduction treatment, thereby increasing the effect of suppressing the oxidation of the surface of the conductive copper particles (A). As a result, the conductive copper particles It becomes easy to suppress the increase in volume resistivity of the conductor film using (A).

As an acid for the pH adjuster, sulfuric acid, nitric acid, hydrochloric acid, or the like may be used in addition to the carboxylic acid soluble in water or alcohols. Hydrochloric acid can adjust the concentration of chloride ions and the pH at the same time. When the dispersion liquid in which the copper particles (a1) are dispersed in the dispersion medium and a compound (such as hydrochloric acid) that generates chloride ions is added has a pH of 3 or less, the dispersion liquid can be used for the reduction treatment as it is.
Moreover, when pH becomes low too much with an acid, pH can be adjusted using a base as a pH adjuster.

The oxidation-reduction potential (ORP) of the reaction system (α) is 220 mV or less, preferably 150 to 220 mV, particularly preferably 180 to 220 mV. If ORP is 220 mV or less, the reduction effect of the oxide film on the surface of the copper particles (a1) is increased, and the surface modification proceeds sufficiently. If the ORP exceeds 220 mV, the surface modification becomes insufficient, and not only the initial volume resistivity is large, but also the change in volume resistivity with time is increased. In this specification, ORP is obtained as a potential difference with respect to the potential of a standard hydrogen electrode (SHE).
The ORP of the reaction system (α) can be adjusted by the type of reducing agent used. Further, it can be adjusted to some extent by a reducing acid such as formic acid.

Examples of the reducing agent include hypophosphorous acid compounds, amine borane compounds, hydrides, and the like.
Examples of hypophosphorous acid compounds include hypophosphorous acid and hypophosphite.
Examples of amine borane compounds include dimethylamine borane.
Examples of the hydride include borohydride salts.
As the reducing agent, hypophosphorous acid, hypophosphite, dimethylamine borane, or borohydride is preferable, and hypophosphorous acid or hypophosphite is particularly preferable.

  As for the usage-amount of a reducing agent, 1 time mole or more is preferable with respect to the whole copper particle (a1), and 1.2 to 10 times mole is more preferable. When the amount of the reducing agent used is at least 1 mol per mole of the entire copper particles (a1), the reducing agent becomes excessively large with respect to the copper on the surface of the copper particles (a1), and the reduction proceeds easily. Moreover, if the usage-amount of a reducing agent is 10 times mole or less with respect to the whole copper particle (a1), it is economically advantageous, and since the quantity of a reducing agent decomposition product decreases, the removal becomes easy.

The reduction reaction may be started by dispersing copper particles (a1) in a dispersion medium and adding a reducing agent to a dispersion in which the concentration and pH of chloride ions are adjusted. The copper particles (a1) may be dispersed in the dispersion medium adjusted and added with the reducing agent.
5-60 degreeC is preferable and, as for the reaction temperature of a reductive reaction, 35-50 degreeC is more preferable. If reaction temperature is below the said lower limit, a reductive reaction will advance easily. If reaction temperature is below the said upper limit, the influence of the density | concentration change of the reaction system ((alpha)) by a dispersion medium evaporating will be small.
After completion of the reduction reaction, the obtained conductive copper particles (A) are separated from the reaction system (α), washed with water or the like as necessary, and then dried to obtain conductive copper particle (A) powder. By-products such as reducing agent decomposition products are soluble in the dispersion medium, and can be separated from the conductive copper particles (A) by a method such as filtration or centrifugation.

(Method for producing conductive copper particles (B))
Examples of the method for producing the conductive copper particles (B) include a method having the following steps (β-1) to (β-3).
(Β-1) In a reaction system containing copper (II) ions and chloride ions, having a pH of 3 or less and an ORP of 220 mV or less (hereinafter referred to as “reaction system (β)”), the copper (II) ions are reduced. And a step of generating secondary particles of copper hydride fine particles (hereinafter referred to as “copper hydride fine particles (b1)”) having an average particle size of 20 to 350 nm.
(Β-2) Copper particles that are primary particles (hereinafter referred to as “copper particles (b2)”) in the reaction system (β) before, during or after the generation of the copper hydride fine particles (b1). The process of adding and producing | generating the copper hydride composite particle (electroconductive copper particle (B)) which added the copper hydride fine particle (b1) to the surface of the copper particle (b2).
(Β-3) A step of separating the conductive copper particles (B) from the reaction system (β).

Step (β-1):
A water-soluble copper compound is dissolved in a solvent, a compound that dissolves in the solvent to produce chloride ions is added, a pH is set to 3 or less, a reducing agent having a redox potential of 220 mV or less is added, and a reaction system is added. (Β) is formed. In the reaction system (β), copper (II) ions are reduced by the reducing agent, and copper hydride fine particles (b1) that are secondary particles containing chlorine atoms in a water-insoluble form are generated. The copper hydride fine particles (b1) are preferably aggregated secondary particles of 20 to 350 nm.

As water-soluble copper compounds, copper sulfate (II), copper nitrate (II), copper formate (II), copper acetate (II), copper chloride (II), copper bromide (II), copper iodide (I) Etc.
The solvent is not particularly limited as long as it dissolves the water-soluble copper compound and is inert to the reducing agent described later. Water or a mixed solvent of water and alcohols (ethanol, isopropyl alcohol, etc.) Water is particularly preferred.
The concentration of the water-soluble copper compound in the reaction system (β) (100% by mass) is preferably 0.1 to 30% by mass. If the density | concentration of a water-soluble copper compound is 0.1 mass% or more, the usage-amount of a solvent can be suppressed and the production | generation efficiency of copper hydride microparticles | fine-particles (b1) will become favorable. When the concentration of the water-soluble copper compound is 30% by mass or less, the yield of the copper hydride fine particles (b1) is improved.

  The concentration of chloride ions in the reaction system (β) is preferably 5 to 100 mass ppm, more preferably 10 to 50 mass based on the total mass of the reaction system (β) for the same reason as in the reaction system (α). ppm is more preferred. The concentration of chloride ions can be adjusted by using a compound that dissolves in a dispersion medium to generate chloride ions. As a compound that generates chloride ions, hydrochloric acid, sodium chloride, potassium chloride, copper (II) chloride, and the like can be used as appropriate.

The pH of the reaction system (β) is 3 or less. When the pH of the reaction system (β) is 3 or less, copper (II) ions and hydrogen ions in the reaction system (β) are reduced by the reducing agent, and the copper hydride fine particles (b1) are sufficiently generated. Moreover, the copper hydride particle | grains (b1) which contain a chlorine atom with a water-insoluble form by producing | generating copper (I) chloride from the copper (I) ion and chloride ion which reduced copper (II) ion Is considered to generate. The pH of the reaction system (β) is more preferably 0.5 to 2 from the viewpoint of the production efficiency of the copper hydride fine particles (b1).
Examples of the acid that adjusts the pH of the reaction system (β) include the same acids as mentioned in the description of the production of the conductive copper particles (A), and oxidation of the surface of the obtained conductive copper particles (B). Formic acid is particularly preferable because the effect of suppressing the increase in volume and the increase in volume resistivity of the conductor film can be easily suppressed.

The redox potential (ORP) of the reaction system (β) is preferably 220 mV or less and 150 to 220 mV. If ORP is 220 mV or less, the reduction effect of copper (II) ions is increased, and copper hydride fine particles (b1) are sufficiently generated. If the ORP exceeds 220 mV, the surface modification becomes insufficient, and not only the initial volume resistivity is large, but also the change in volume resistivity with time increases.
Examples of the reducing agent are the same as those described in the description of the production of the conductive copper particles (A), and hypophosphorous acid, hypophosphite, dimethylamine borane, or borohydride is preferable. Hypophosphorous acid or hypophosphite is particularly preferred.

  The addition amount of the reducing agent is preferably 1.2 to 10 times the molar amount of the water-soluble copper compound to be used. If the addition amount of the reducing agent is 1.2 times mol or more with respect to the water-soluble copper compound, the reduction reaction proceeds smoothly. If the addition amount of the reducing agent is 10 times mol or less with respect to the water-soluble copper compound, the amount of impurities (sodium, boron, phosphorus, etc.) contained in the copper hydride fine particles (b2) can be easily suppressed.

  The reaction system (β) includes a reducing agent solution in which a reducing agent is dissolved in a solvent such as water, and a solution in which a water-soluble copper compound is dissolved in a solvent such as water (hereinafter referred to as “water-soluble copper compound solution”). It may be formed by mixing, or may be formed by adding a solid state reducing agent such as powder to the water-soluble copper compound solution.

The reaction system (β) means a system in which copper hydride fine particles are produced. Specifically, a reducing agent is added to a water-soluble copper compound solution containing copper (II) ions and chloride ions and having a pH of 3 or less. Immediately after the addition, a system in which the formation reaction of the copper hydride fine particles (b1) has not yet progressed, a system in which the formation reaction of the copper hydride fine particles (b1) is in progress, and the copper hydride fine particles (b1) It means a system in which the production reaction is completed and the produced copper hydride fine particles (b1) are dispersed. In the reaction system (β), the solvent of the water-soluble copper compound solution, the water-soluble copper compound dissolved in the solvent (substantially ionized, and present as a copper (II) ion, a counter anion, etc.) ), A compound that produces chloride ions (substantially ionized and exists as chloride ions and paired cations, etc.), ions and residues after copper hydride fine particles (b1) are produced, There exist reducing agents and their decomposition products.
For example, when the produced copper hydride fine particles (b1) are isolated and newly dispersed in a dispersion medium to form a dispersion, the copper hydride fine particles (b1) in the dispersion are present in the reaction system (β). Not the copper hydride fine particles (b1).

  The reaction temperature of the reaction system (β) is preferably 60 ° C. or lower, more preferably 5 to 60 ° C., and particularly preferably 20 to 50 ° C. Although copper hydride has a property of being decomposed by heating, if the reaction temperature of the reaction system (β) is equal to or lower than the upper limit value, it is easy to suppress decomposition of the copper hydride fine particles (b2). When the reaction temperature of the reaction system (β) is equal to or higher than the lower limit, the reduction reaction easily proceeds.

Step (β-2):
Copper hydride in which copper particles (b2), which are primary particles, are added to the reaction system (β) formed in step (β-1), and copper hydride fine particles (b1) are attached to the surfaces of the copper particles (b2). Composite particles (conductive copper particles (B)) are generated. The copper particles (b2) added in the step (β-2) are reduced in surface oxide film in the reaction system (β), and contain chlorine atoms in a water-insoluble form. Then, copper hydride particles (b1) containing water-insoluble chlorine atoms adhere.

  The addition time of the copper particles (b2) to the reaction system (β) is before the production of the copper hydride fine particles (b1), during the production of the copper hydride fine particles (b1), or after the production of the copper hydride fine particles (b1). It is. Adding the copper particles (b2) to the reaction system (β) before the formation of the copper hydride fine particles (b1) means that the copper particles (b2) already exist when the reaction system (β) is formed. Means. For example, there may be mentioned a case where a reaction system (β) is formed by adding a reducing agent after adding copper particles (b2) to a water-soluble copper compound solution. Further, adding the copper particles (b2) to the reaction system (β) after the production of the copper hydride fine particles (b1) means that new production of the copper hydride fine particles (b1) does not occur and has already been produced. This means that the copper particles (b2) are added to the reaction system (β) in a state where no further growth of the copper hydride fine particles (b1) is occurring. For example, the case where the copper particles (b2) are added after the copper ions and the reducing agent in the reaction system (β) are consumed and the production reaction of the copper hydride fine particles (b1) does not occur.

  The addition of the copper particles (b2) to the reaction system (β) is easy to obtain conductive copper particles (B) having a low volume resistivity, or before the formation of the copper hydride fine particles (b1) or the copper hydride. During the production of the fine particles (b1) is preferable. Before and during the production of the copper hydride fine particles (b1), copper (II) ions are present in the reaction system (β). By adding copper particles (b2) in the presence of copper (II) ions in the reaction system (β), copper (II) in a state where the copper particles (b2) and copper hydride fine particles (b1) coexist. ) Since the ions can be reduced, the copper particles (b2) and the copper hydride fine particles (b1) are bonded more firmly. The presence of copper (II) ions can be grasped by a copper ion electrode, ultraviolet / visible spectrum analysis, and a method of measuring copper atom concentration by atomic emission spectrum.

Examples of the copper particles (b2) to be added to the reaction system (β) include the same copper particles as the copper particles (a1) described in the production of the conductive copper particles (A), and the average particle diameter (average primary particles). Copper particles having a diameter of 1 to 20 μm are preferable.
The content of copper particles (b2) in the reaction system (β) is the content of copper (II) ions in the water-soluble copper compound solution before adding the reducing agent (all the water-soluble copper compounds are ionized). 1-100 mass parts is preferable with respect to 100 mass parts, and 5-100 mass parts is more preferable.

Step (β-3):
The produced | generated electroconductive copper particle (B) is isolate | separated from a reaction system ((beta)), and the particle | grains of a powder state are obtained. The method for separating the conductive copper particles (B) is not particularly limited, and examples thereof include centrifugation and filtration.
The separated conductive copper particles (B) are preferably washed with a cleaning liquid such as water to remove soluble impurities attached to the conductive copper particles (B). Prior to separation, the solvent of the reaction system (β) and impurities dissolved in the solvent (anion of water-soluble copper compound, decomposition product of reducing agent, etc.) are removed by solvent substitution or the like. Also good.

(Method for producing conductive copper particles (C))
Examples of the method for producing the conductive copper particles (C) include a method having the following steps (γ-1) and (γ-2).
(Γ-1) In a reaction system containing copper (II) ions and chloride ions, having a pH of 3 or less and an ORP of 220 mV or less (hereinafter referred to as “reaction system (γ)”), the copper (II) ions are reduced. The process of producing | generating the copper hydride microparticles | fine-particles (electroconductive copper particle (C)) which are secondary particles and whose average particle diameter is 10 nm-1 micrometer.
(Γ-2) A step of separating the conductive copper particles (C) from the reaction system (γ).

Step (γ-1):
The step (γ-1) can be carried out by the same method as the step (β-1) in the production of the conductive copper particles (B) except for the following preferable conditions.
The average particle diameter of the secondary particles of the conductive copper particles (C) produced in the reaction system (γ) is preferably 10 nm to 1 μm. The average particle diameter of the conductive copper particles (C) can be adjusted by controlling the reaction temperature and reaction time and adding a dispersant.

Step (γ-2):
The step (γ-2) can be performed in the same manner as the step (β-3) in the production of the conductive copper particles (B).

(Method for producing conductive copper particles (D))
As a method for producing the conductive copper particles (D), the conductive copper particles (B) are produced, the obtained conductive copper particles (B) are heated, and the copper hydride in the conductive copper particles (B) is produced. There is a method in which the fine particles (b1) are converted into metal copper fine particles to obtain conductive copper particles (D).
In this case, the copper fine particles produced by converting the copper hydride of the copper hydride fine particles (b1) into metal copper are not peeled off from the surfaces of the copper particles (b2) as the primary particles. Further, there is substantially no difference between the size of the copper hydride fine particles (b1) before heating and the size of the produced copper fine particles. Therefore, the conductive copper particles (D) having substantially the same structure and the same average particle diameter as the conductive copper particles (B) can be obtained.

  The heating temperature is preferably 60 to 120 ° C, more preferably 60 to 100 ° C, and still more preferably 60 to 90 ° C. If heating temperature is more than the said lower limit, heating time can be shortened and manufacturing cost can be suppressed. If heating temperature is below the said upper limit, it will be easy to suppress copper fine particles, and it will be easy to suppress the increase in the volume resistivity of a conductor film.

  The pressure during heating of the conductive copper particles (B) is preferably −101 to −50 kPa (gauge pressure). If the pressure at the time of heating is −101 kPa or more, a large-scale apparatus is not required, and it becomes easy to remove excess solvent and dry. If the pressure at the time of a heating is -50kPa or less, time can be shortened and manufacturing cost can be suppressed.

(Method for producing conductive copper particles (E))
As a method for producing the conductive copper particles (E), the conductive copper particles (C) are produced, the obtained conductive copper particles (C) are heated, and the copper hydride in the conductive copper particles (C) is produced. Can be converted into metallic copper to obtain conductive copper particles (E). In this case, there is substantially no difference between the size of the conductive copper particles (C) before heating and the size of the conductive copper particles (E) generated by heating.
The heating conditions for the conductive copper particles (C) can be the same as the heating conditions for the conductive copper particles (B) in the method for producing the conductive copper particles (D).

<Conductor forming composition>
The composition for forming a conductor of the present invention includes the conductive copper particles of the present invention and a solvent as essential components, and a resin binder as necessary.
The conductive copper particles are preferably one or more selected from the group consisting of the conductive copper particles (A) to (E). The conductive copper particles (A), the conductive copper particles (B) and the conductive copper are preferable. One or more types selected from the group consisting of particles (D) are more preferable, and any of conductive copper particles (A), conductive copper particles (B), and conductive copper particles (D) is particularly preferable.

  Examples of the solvent include cyclohexanone, cyclohexanol, terpineol, ethylene glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether. , Diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate and the like.

  The content of the solvent in the composition for forming a conductor is preferably 1 to 20% by mass with respect to the conductive copper particles (100% by mass) from the viewpoint that it can be easily adjusted to a viscosity suitable for a printing paste or the like.

As a resin binder, the well-known thermosetting resin binder used for a metal paste, a thermoplastic resin binder, etc. are mentioned. It is preferable to use a thermosetting resin binder that sufficiently undergoes a curing reaction at the temperature during curing. Further, it is preferable to use a thermoplastic resin binder that has a small tack and can maintain the shape of the conductor in the use environment.
Examples of the resin binder include phenol resin, melamine resin, urea resin, diallyl phthalate resin, unsaturated alkyd resin, epoxy resin, urethane resin, bismaleidotriazine resin, silicone resin, acrylic resin, and polyester resin. Of these, a phenol resin and a polyester resin are preferable, and a phenol resin is particularly preferable.

If the amount of the cured or solidified resin binder is too large, contact between the conductive copper particles is hindered, and the volume resistivity of the conductor film is increased. Therefore, the content of the resin binder in the conductor-forming composition needs to be within a range in which the amount of the cured product or solidified product does not hinder the conductivity of the conductive copper particles.
The content of the resin binder in the composition for forming a conductor can be appropriately selected in consideration of the ratio between the volume of the conductive copper particles and the gap formed between the conductive copper particles. 5-50 mass parts is preferable with respect to part, and 5-20 mass parts is more preferable. If content of a resin binder is more than the said lower limit, the hardness of a conductor film will become more favorable. If content of a resin binder is below the said upper limit, it will be easy to suppress the volume resistivity of a conductor film low.

  If the composition for conductor formation of this invention is a range which does not impair the effect of this invention, various additives (a leveling agent, a coupling agent, a viscosity modifier, antioxidant, etc.) etc. as needed. May be included.

[Production method]
The conductor-forming composition of the present invention can be prepared by mixing the conductive copper particles of the present invention, a solvent, and a resin binder used as necessary. When mixing a thermosetting resin binder among the resin binders, heating may be performed to such an extent that the thermosetting resin binder does not cure and the solvent does not volatilize and disappear. If necessary, mixing may be performed by replacing the inside of the mixing container with an inert gas. Thereby, it becomes easy to suppress the oxidation of the conductive copper particles being mixed.

  The conductor forming composition of the present invention described above contains the conductive copper particles of the present invention that are not easily oxidized even in the air, so that the volume resistivity is low and the volume resistivity is low. A conductor film that changes little over time can be formed.

<Substrate with conductor>
The base material with a conductor of the present invention has a base material and a conductor film formed on the base material by the conductor forming composition of the present invention. As for the base material with a conductor of this invention, it is preferable that a conductor film is a linear wiring body, and it is preferable that it is a printed wiring board.
Examples of the substrate include a glass substrate, a plastic substrate (a film-like substrate such as a polyimide film and a polyester film), a substrate made of a fiber reinforced composite material (a glass fiber reinforced resin substrate, etc.), and a ceramic substrate. Examples thereof include materials and metal substrates.

The volume resistivity of the conductor film is preferably 1.0 × 10 ⁻⁴ Ωcm or less. When the volume resistivity is 1.0 × 10 ⁻⁴ Ωcm or less, the substrate with a conductor of the present invention can be suitably used as a conductor for electronic equipment. The volume resistivity of the conductor film is measured with a four-probe resistance meter.
Further, the change rate of the volume resistivity after one month with respect to the volume resistivity immediately after the film formation in the conductor film is preferably 5% or less, and more preferably 2% or less.

  The thickness of the conductor film is preferably 1 to 100 μm and particularly preferably 5 to 50 μm from the viewpoint that it is easy to maintain the wiring shape while ensuring stable conductivity.

[Production method]
The substrate with a conductor of the present invention is formed by coating the surface of the substrate with the composition for forming a conductor of the present invention to form a coating layer, and removing a volatile component such as a solvent from the coating layer. It can be manufactured by forming a body membrane. Moreover, when the composition for forming a conductor of the present invention contains a thermosetting resin binder, after removing volatile components such as a solvent from the coating layer, the conductor film is formed by curing the thermosetting resin binder. Form. In this case, the obtained conductor film includes conductive copper particles and a cured product of a thermosetting resin binder. Moreover, when the composition for conductor formation of this invention contains a thermoplastic resin binder, a conductor film is formed by removing volatile components, such as a solvent, from an application layer. In this case, the obtained conductive film contains conductive copper particles and a solid thermoplastic resin.

  Examples of the method for applying the composition for forming a conductor include known methods such as screen printing, roll coating, air knife coating, blade coating, bar coating, gravure coating, die coating, and slide coating. .

When the composition for forming a conductor includes a thermosetting resin binder, the thermosetting resin binder can be cured by heating. Examples of the heating method include hot air heating and heat radiation. The heating temperature and the heating time can be appropriately determined according to the characteristics required for the conductor film. When the composition for forming a conductor contains conductive copper particles (B) or conductive copper particles (C) as conductive copper particles, the conductive copper and the conductive copper are cured simultaneously with the curing of the thermosetting resin binder. Copper hydride contained in the particles is converted into metallic copper.
When the composition for forming a conductor includes a thermoplastic resin binder, and the conductive copper particles include conductive copper particles (B) or conductive copper particles (C), volatilization of a solvent or the like The copper hydride contained in these electroconductive copper particles is converted into metallic copper by the heating at the time of removing the sex component.

The heating temperature is preferably 100 to 300 ° C. If heating temperature is 100 degreeC or more, the solvent contained in the composition for conductor formation will fully volatilize. Further, the curing of the thermosetting resin is likely to proceed. If heating temperature is 300 degrees C or less, a plastic film can be used as a base material which forms a conductor film. The curing time may be a time for the resin binder to sufficiently cure depending on the curing temperature.
The environment in which the conductor film is formed is not particularly limited, and may be in air or under nitrogen with little oxygen. Among these, air is preferable because the production equipment is simplified.

  The base material with a conductor of the present invention described above has a conductor film having a low volume resistivity and a small change with time in volume resistivity.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description. Examples 1 to 5 are examples, and examples 6 to 10 are comparative examples.

[Measuring method]
The measuring method of each numerical value in a present Example is shown below.

(Average particle size)
The average particle diameter of the copper particles before the reduction treatment and the obtained conductive copper particles was measured as follows. In the case of primary particles, the particle diameters of 100 particles randomly selected from SEM images obtained by SEM (manufactured by Hitachi, Ltd., S-4300) were measured and calculated by averaging. In the case of secondary particles, the particle size of 100 particles randomly selected from a TEM image obtained with a transmission electron microscope (TEM) was measured and calculated by averaging.

(Reaction system chloride ion concentration)
The chloride ion concentration in the reaction system was measured with a chlorine ion electrode (HM-20P, manufactured by Toa DKK Corporation).

(PH of reaction system)
The pH of the reaction system was measured with a pH meter (manufactured by Toa DKK Corporation, HM-20P).

(Redox potential of reaction system)
The oxidation-reduction potential (ORP) of the reaction system was measured with an ORP meter (RM-12P, manufactured by Toa DKK Corporation).

(Chlorine atom content of conductive copper particles)
The content of chlorine atoms in the obtained conductive copper particles was determined by fluorescent X-ray analysis (manufactured by Rigaku Corporation, ZSX100e).

(Surface oxygen content of conductive copper particles)
The surface oxygen content of the obtained conductive copper particles was determined by determining the surface oxygen concentration [atomic%] and the surface copper concentration [atomic%] by X-ray photoelectron spectroscopy (manufactured by ULVAC-PHI, ESCA5500). It was calculated by dividing by the surface copper concentration.

(Water solubility test of chlorine atoms in conductive copper particles)
When all the chlorine atoms contained in the conductive copper particles are eluted in the distilled water, the conductive copper particles in such an amount that the concentration of chloride ions in the distilled water is 100 ppm by weight are added to the distilled water (dissolved oxygen concentration). 1 mass ppm or less). Next, the distilled water in which the conductive copper particles are immersed is stirred at 20 ° C. for 5 seconds at 1000 rpm using a test tube mixer (manufactured by ASONE, HM-01), and then the chloride ions eluted in the distilled water. The concentration was measured using a chlorine ion electrode.

(Conductor film thickness)
The thickness of the conductor film was measured with DEKTAK3 (manufactured by Veeco metrology group).

(Surface resistance value of conductor film)
The surface resistance value of the conductor film was measured immediately after film formation with a four-probe resistance meter (manufactured by Mitsubishi Yuka Co., Ltd., model: lorestaIP MCP-T250). Moreover, the surface resistance value of the conductor film after one month passed was measured again, and the change rate (unit:%) with respect to the surface resistance value immediately after film formation was determined.

(Volume resistivity of conductor film)
The volume resistivity was determined by taking the product of the thickness of the conductor film and the surface resistance value of the conductor film measured by the above method.

[Example 1]
(Production of conductive copper particles A1)
In a glass beaker, 100 g of copper particles (trade name “1400YP”, average primary particle size: 7 μm, manufactured by Mitsui Mining & Smelting Co., Ltd.) are dispersed in 1800 g of distilled water, 30 g of formic acid as a pH adjuster, and chloride As a compound that generates ions, 35 mass% hydrochloric acid was added to adjust the chloride ion concentration of the reaction system to 10 massppm. Next, the beaker was placed in a 40 ° C. water bath, 180 g of a 50 mass% hypophosphorous acid aqueous solution was added with stirring to form a reaction system (α), and stirring was continued for 30 minutes. Table 1 shows the pH of the reaction system (α) immediately after the addition of hypophosphorous acid, the pH of the reaction system (α) after the completion of the reaction, and the redox potential (ORP) of the reaction system (α) after the completion of the reaction. Show.

After completion of the stirring, the precipitate was separated by filtration. The precipitate was redispersed in 600 g of distilled water, and then the aggregate was precipitated again by centrifugation to separate the precipitate. Under reduced pressure of −35 kPa (gauge pressure), the precipitate was heated at 80 ° C. for 60 minutes to volatilize and remove residual water, thereby obtaining conductive copper particles A1.
Content of the chlorine atom in electroconductive copper particle A1 was 100 mass ppm. Moreover, when the water solubility test of electroconductive copper particle A1 was implemented, the density | concentration of the chloride ion eluted in distilled water was less than 5 mass ppm. That is, the chlorine atom contained in the conductive copper particles A1 was in a water-insoluble form. Moreover, the average particle diameter of electroconductive copper particle A1 was 7 micrometers.

(Preparation of composition for forming conductor film)
1.2 g of conductive copper particles A1 was added to a resin solution in which 0.26 g of phenol resin (trade name “Resitop PL 6220” manufactured by Gunei Chemical Co., Ltd.) was dissolved in 0.15 g of ethylene glycol monobutyl ether acetate. . This mixture was put in a mortar and mixed at room temperature to obtain a conductor film forming composition. The addition amount of the phenol resin was 11 parts by mass with respect to 100 parts by mass of the conductive copper particles A1.

(Formation of conductor film)
The obtained composition for forming a conductor film is applied to a glass substrate and heated at 150 ° C. for 1 hour to cure the phenol resin, thereby forming a conductor film having a thickness of 20 μm, and the volume resistivity of the conductor film Was measured.

[Example 2]
(Production of conductive copper particles A2)
Conductive copper particles A2 were obtained in the same manner as in Example 1 except that the chloride ion concentration in the reaction system (α) was 25 ppm by mass.
Content of the chlorine atom of obtained electroconductive copper particle A2 was 250 mass ppm. Moreover, when the water solubility test of electroconductive copper particle A2 was implemented, the density | concentration of the chloride ion eluted in distilled water was less than 5 mass ppm. That is, the chlorine atom contained in the conductive copper particles A2 was in a water-insoluble form. Moreover, the average particle diameter of electroconductive copper particle A2 was 7 micrometers.

(Preparation of composition for forming conductor film)
A conductive film forming composition was obtained in the same manner as in Example 1 using the conductive copper particles A2.

(Formation of conductor film)
Using the obtained composition for forming a conductor film, a conductor film was formed in the same manner as in Example 1, and its volume resistivity was measured.

[Example 3]
(Production of conductive copper particles D1)
In a glass beaker, 100 g of copper particles (manufactured by Mitsui Kinzoku Mining Co., Ltd., trade name “1400YP”, average primary particle diameter: 7 μm) was dispersed in 1800 g of distilled water. Next, 15 g of formic acid as a pH adjuster, 39 g of copper formate as a water-soluble copper compound, and 35% by mass hydrochloric acid as a compound that generates chloride ions are added, and the chloride ion concentration of the reaction system is 10 masses. ppm. Next, the beaker was placed in a 40 ° C. water bath, 180 g of a 50 mass% hypophosphorous acid aqueous solution was added with stirring to form a reaction system (β), and stirring was continued for 30 minutes. After the stirring, the reaction system (β) was treated in the same manner as the reaction system (α) of Example 1 to obtain conductive copper particles D1. In this example, conductive copper particles B1 having a form in which copper hydride fine particles as secondary particles adhere to the surface of copper particles as primary particles are once generated, and in order to volatilize residual moisture, the conductive copper particles B1 are vaporized at 80 ° C. for 60 minutes. In the process of heating, it is considered that the copper hydride fine particles are converted into copper fine particles to obtain conductive copper particles D1.
Content of the chlorine atom of the obtained electroconductive copper particle D1 was 150 mass ppm. Moreover, when the water solubility test of the electroconductive copper particle D1 was implemented, the density | concentration of the chloride ion eluted in distilled water was less than 5 mass ppm. That is, the chlorine atom contained in the conductive copper particles D1 was in a water-insoluble form. Moreover, the average particle diameter of the conductive copper particles D1 was 8 μm.

(Preparation of composition for forming conductor film)
1.2 g of conductive copper particles D1 was added to a resin solution in which 0.15 g of an amorphous polyester resin (trade name “Byron 300” manufactured by Toyobo Co., Ltd.) was dissolved in 0.35 g of cyclohexanone. This mixture was put in a mortar and mixed at room temperature to obtain a conductor film forming composition. The addition amount of the amorphous polyester resin was 11 parts by mass with respect to 100 parts by mass of the conductive copper particles D1.

(Formation of conductor film)
The obtained composition for forming a conductor film is applied to a glass substrate, heated at 150 ° C. for 1 hour to cure the amorphous polyester resin, and a conductor film having a thickness of 20 μm is formed. The volume resistivity of was measured.

[Example 4]
(Production of conductive copper particles D2)
Conductive copper particles D2 were obtained in the same manner as in Example 3 except that the chloride ion concentration in the reaction system (β) was 15 ppm by mass.
Content of the chlorine atom of the obtained electroconductive copper particle D2 was 400 mass ppm. Moreover, when the water solubility test of the electroconductive copper particle D2 was implemented, the density | concentration of the chloride ion eluted in distilled water was 8 mass ppm. That is, the chlorine atom contained in the conductive copper particles D2 was in a water-insoluble form. Moreover, the average particle diameter of the electroconductive copper particle D2 was 8 micrometers.

(Preparation of composition for forming conductor film)
A conductive film forming composition was obtained in the same manner as in Example 3 using the conductive copper particles D2.

(Formation of conductor film)
Using the obtained composition for forming a conductor film, a conductor film was formed in the same manner as in Example 1, and its volume resistivity was measured.

[Example 5]
(Production of conductive copper particles D3)
Conductive copper particles D3 were obtained in the same manner as in Example 3 except that the chloride ion concentration in the reaction system (β) was 25 ppm by mass.
Content of the chlorine atom of the obtained electroconductive copper particle B3 was 700 mass ppm. Moreover, when the water solubility test of the electroconductive copper particle D3 was implemented, the density | concentration of the chloride ion eluted in distilled water was 10 mass ppm. That is, the chlorine contained in the conductive copper particles D3 was in a water-insoluble form. Moreover, the average particle diameter of the electroconductive copper particle D3 was 8 micrometers.

(Preparation of composition for forming conductor film)
A conductive film forming composition was obtained in the same manner as in Example 3 using the conductive copper particles D3.

(Formation of conductor film)
Using the obtained composition for forming a conductor film, a conductor film was formed in the same manner as in Example 1, and its volume resistivity was measured.

[Example 6]
(Manufacture of conductive copper particles)
In a glass beaker, 100 g of copper particles (trade name “1400YP”, average primary particle diameter: 7 μm, manufactured by Mitsui Mining & Mining Co., Ltd.) are dispersed in 1800 g of distilled water, 30 g of formic acid is added, and then 40 beakers are added. Conductive copper particles F1 were obtained in the same manner as in Example 1 except that the reaction system was formed by adding 90 g of sulfuric acid while stirring in a water bath at ° C.
Content of the chlorine atom of the obtained electroconductive copper particle F1 was less than 50 mass ppm.

(Preparation of composition for forming conductor film)
A conductive film forming composition was obtained in the same manner as in Example 1 using the conductive copper particles F1.

(Formation of conductor film)
Using the obtained composition for forming a conductor film, a conductor film was formed in the same manner as in Example 1, and its volume resistivity was measured.

[Example 7]
(Manufacture of conductive copper particles)
In a glass beaker, 100 g of copper particles (trade name “1400YP”, average primary particle size 7 μm, manufactured by Mitsui Mining & Mining Co., Ltd.) are dispersed in 1800 g of distilled water, and the beaker is placed in a 40 ° C. water bath. Conductive copper particles F2 were obtained in the same manner as in Example 1 except that 72 g of formic acid was added while stirring to form a reaction system.
Content of the chlorine atom of the obtained electroconductive copper particle F2 was less than 50 mass ppm.

(Preparation of composition for forming conductor film)
A conductive film-forming composition was obtained in the same manner as in Example 1 using the conductive copper particles F2.

(Formation of conductor film)
Using the obtained composition for forming a conductor film, a conductor film was formed in the same manner as in Example 1, and its volume resistivity was measured.

[Example 8]
(Manufacture of conductive copper particles)
In a glass beaker, 100 g of copper particles (trade name “1400YP”, average primary particle diameter: 7 μm, manufactured by Mitsui Mining & Smelting Co., Ltd.) are dispersed in 1800 g of distilled water, and 35 mass% hydrochloric acid is added to add chlorine in the reaction system. Conductive copper particles F3 were formed in the same manner as in Example 1 except that the atomic concentration was 100 ppm by mass, the beaker was placed in a 40 ° C. water bath, and 72 g of formic acid was added while stirring to form a reaction system. Got.
The obtained copper content of conductive copper particles F3 was 300 mass ppm. Moreover, when the water solubility test of the electroconductive copper particle F3 was implemented, the density | concentration of the chloride ion eluted in distilled water was 30 mass ppm. That is, the chlorine contained in the conductive copper particles F3 was in a water-soluble form.

(Preparation of composition for forming conductor film)
A conductive film forming composition was obtained in the same manner as in Example 1 using the conductive copper particles F3.

(Formation of conductor film)
Using the obtained composition for forming a conductor film, a conductor film was formed in the same manner as in Example 1, and its volume resistivity was measured.

[Example 9]
(Manufacture of conductive copper particles)
After obtaining conductive copper particles in the same manner as in Example 7, hydrochloric acid was added to the conductive copper particles so that the chlorine atom content was 100 ppm by mass to obtain conductive copper particles F4.
Content of the chlorine atom of the obtained electroconductive copper particle F4 was 100 mass ppm. Moreover, when the water solubility test of the electroconductive copper particle F4 was implemented, the density | concentration of the chloride ion eluted in distilled water was 90 mass ppm. That is, the chlorine contained in the conductive copper particles F4 was in a water-soluble form.

(Preparation of composition for forming conductor film)
A conductive film forming composition was obtained in the same manner as in Example 1 using the conductive copper particles F4.

(Formation of conductor film)
Using the obtained composition for forming a conductor film, a conductor film was formed in the same manner as in Example 1, and its volume resistivity was measured.

[Example 10]
(Preparation of conductive copper particles)
After obtaining conductive copper particles in the same manner as in Example 7, hydrochloric acid was further added to the conductive copper particles so that the chlorine atom content was 1,000 ppm by mass to obtain conductive copper particles F5. It was.
Content of the chlorine atom of the obtained electroconductive copper particle F5 was 1,000 mass ppm. Moreover, when the water solubility test of the electroconductive copper particle F5 was implemented, the density | concentration of the chloride ion eluted in distilled water was 90 mass ppm. That is, the chlorine contained in the conductive copper particles F5 was in a water-soluble form.

(Preparation of composition for forming conductor film)
A conductive film forming composition was obtained in the same manner as in Example 1 using the conductive copper particles F5.

(Formation of conductor film)
Using the obtained composition for forming a conductor film, a conductor film was formed in the same manner as in Example 1, and its volume resistivity was measured.
Table 1 shows the characteristics of the reaction system, conductive copper particles, and conductor film in Examples 1 to 10 and the evaluation results.

  As shown in Table 1, Examples 6 and 7 using conductive copper particles having a chlorine atom content of less than 50 ppm by mass, and Example 8 using conductive copper particles containing chlorine atoms in a water-soluble form. The conductive film of 1 to 10 had a high volume resistivity immediately after the film formation, or the volume resistivity increased by storage even though the volume resistivity immediately after the film formation was low. On the other hand, the conductor films of Examples 1 to 5 using the conductive copper particles of the present invention containing 50 to 1000 mass ppm of chlorine atoms in a water-insoluble form have a low volume resistivity, and the month The rate of change after the lapse was also low.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope and spirit of the invention.
This application is based on Japanese Patent Application No. 2010-226632 filed on Oct. 6, 2010, the contents of which are incorporated herein by reference.

  The conductive copper particles and the conductive film forming composition of the present invention are used for various purposes such as formation and repair of wiring patterns in printed wiring boards, interlayer wiring in semiconductor packages, bonding of printed wiring boards and electronic components, etc. Can be suitably used.

Claims (1)

The chlorine atom is contained in an amount of 80 to 1000 ppm by mass with respect to the total mass of the particle, the chlorine atom is present in a water-insoluble form, and the surface oxygen concentration relative to the surface copper concentration (unit: atomic%) of the particle ( A method for producing conductive copper particles having a surface oxygen amount represented by a ratio of (unit: atomic%) of 0.5 or less ,
A method for producing conductive copper particles, comprising a step of reducing at least one of copper particles and copper (II) ions in a reaction system containing chloride ions, having a pH of 3 or less and an oxidation-reduction potential of 220 mV or less.